Comparative analysis of stability and removal torque of custom CAD-CAM versus stock abutments before and after cyclic loading: A systematic review with meta-analysis and GRADE analysis.

STATEMENT OF PROBLEM: Advancements in computer-aided design and computer-aided manufacturing (CAD-CAM) have enabled greater precision and customization in implant abutment fabrication. However, current evidence remains limited regarding the comparative mechanical stability and torque retention of stock versus CAD-CAM-fabricated abutments, particularly under dynamic loading conditions. PURPOSE: The purpose of this study was to compare the stability and removal torque values of custom CAD-CAM abutments and stock abutments before and after dynamic loading. MATERIAL AND METHODS: This systematic review was registered on PROSPERO (CRD42025634444) and conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A comprehensive electronic search was performed across the PubMed, Scopus, EBSCOhost, and Google Scholar databases for studies published between January 2010 and November 2025. Only English-language in vitro studies evaluating removal torque values for stock versus CAD-CAM abutments were included. Data extraction and meta-analysis were performed using the Review Manager (RevMan; version 5.4; Cochrane Collaboration) software program. Risk of bias was assessed using the Quality Assessment Tool for In Vitro Studies (QUIN), and certainty of evidence was evaluated using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach on the GRADEpro platform. A leave-one-out sensitivity analysis was conducted to assess the robustness of the pooled estimates. Standardized mean differences (SMDs) with 95% confidence intervals (CIs) were calculated under a random-effects model. Heterogeneity was assessed using the I² statistic, and statistical significance was defined at α=.05 (P<.05). RESULTS: Among 1222 identified studies, 5 met the inclusion criteria for qualitative synthesis and 4 for meta-analysis, comprising 107 implant-abutment assemblies. Meta-analysis revealed significantly higher removal torque values for stock abutments compared with CAD-CAM abutments both before (SMD=-0.91; 95% CI: -1.56 to -0.26; P=.006) and after (SMD=-1.05; 95% CI: -1.87 to -0.23; P=.01) cyclic loading. Moderate heterogeneity was observed (I²=54%). The overall certainty of evidence was rated as very low. CONCLUSIONS: Despite better customization, CAD-CAM abutments demonstrated greater torque reduction compared with stock abutments both before and after dynamic loading, suggesting reduced preload maintenance under functional stresses. Further long-term clinical studies are required to validate these in vitro findings.